In this article, we will discuss the earth’s interior and the internal layers of the earth.
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The surface of the earth is an outcome of the processes operating in the interior of the earth. Both exogenic and endogenic forces are constantly shaping the landscape of Earth. It is fascinating to know how scientists have gathered information about the different layers of the Earth.
The radius of the earth is about 6370km. Till now, no one can reach the centre of the earth. Most of our knowledge about the earth’s interior is based on the estimates and inferences. However, the study of seismic waves has contributed immensely to our understanding of the different layers of the earth. For instance, the velocity and the path travelled by the waves provide the authenticity of the physical conditions prevailing inside the earth.
Sources of information about the layers of the earth
The average density of the upper mantle is about 4.5 gm/cm3.
The average temperature of this layer is about 1100 C ⁰.
The Repetti Discontinuity separates the upper mantle from the lower mantle.
Due to Repetti discontinuity, there is a sharp increase in the velocity of the seismic waves.
The upper mantle is heterogeneous in terms of density and composition.
The thickness of the uppermost part of this stratum is about 80-100 km.
The uppermost part of the upper mantle is as rigid as the crust.
Both crust and upper mantle constitute the Lithosphere.
The asthenosphere is that part of the layer of earth which is below the Lithosphere. It extends at a depth of 100 km to 400 km from the lithosphere. Due to the high temperature, this region is partially molten. Here the velocity of seismic wave slowdowns abruptly. This region is called Low-velocity region. Also, it is rich in Peridotite. Moreover, this region is popularly known as the Magma Chamber.
The lower mantle extends at a depth of 670 km to 2900km.
The average density of this region is about 6.5gm/cm3.
It is composed of Olivine, Plagioclase and Orthoclase minerals.
Guttenberg Discontinuity separates the lower mantle and the upper core of the earth.
At the depth of 2900 km to 6371 km, lies the core of the earth. Because of metallic composition, its density is nearly twice as the mantle. It comprises of 15% to 16% of the total volume of the earth. The core is divided into two regions called the outer core and the inner core.
It extends between 2900 km to 5150 km.
The density of the outer core is about 10gm/cm3.
It mainly consists of Iron and Nickle (about 85%).
The outer core is always in the molten state.
Lehman Discontinuity separates the outer core and the inner-core.
The inner-core extends between 5150 km to 6371 km.
The average density of the inner core is about 13gm/cm3.
Despite the high temperature, the inner-core is always in the solid-state due to very high pressure prevailing in this region.
The temperature of the inner core is about 6000 C⁰.
Frequently asked Questions-
The asthenosphere is part of which layer?
The asthenosphere is the part of Upper mantle layer of the earth.
Layers which are solid?
The crust and the inner core.
What is the location of Conrad discontinuity?
The location of Conrad discontinuity is between the oceanic crust and the continental crust.
What is the location of Moho discontinuity?
The location of Moho discontinuity is between the crust and the mantle layer of the earth.
Location of Repetti discontinuity?
The Repettis discontinuity is located between the upper and the lower mantle. The sharp increase in the velocity of the seismic wave is indicative of the existence of this discontinuity.
What is the location of Guttenburg discontinuity?
Between the lower mantle and outer core of the earth. Here, the velocity of P( primary) waves decreases abruptly. On the other hand, the S (Secondary) waves disappear beyond this discontinuity.
What is the location of Lehman discontinuity?
It is located between the outer and the inner core of the earth. The increase in the velocity of P waves shows the existence of this discontinuity.
Which layer of the Earth has thermal convectional currents?
The thermal convectional currents are common in the Mantle layer of the earth.